Radars using millimeter waves having a wavelength of 1 to 10 mm (frequency: 30 to 300 GHz) (so-called millimeter-wave radars) have been known as one of radar transceivers to be mounted on vehicles and capable of detecting surrounding objects. Since the millimeter-wave radars use a radio wave, the millimeter-wave radars have an advantage of ensuring a certain sensitivity even under bad weather conditions, such as rain and fog. The millimeter-wave radar can obtain information about its surrounding environment (such as a position (distance, direction and/or the like) and a relative velocity of a detection target object (hereinafter, referred to as “target object”)) by transmitting a transmission signal (radio wave) around an automobile, receiving a reflection signal (reflected wave) reflected from the target object, and analyzing the reflection signal.
Furthermore, in recent years, high-resolution millimeter-wave radars using a 79 GHz band (77 to 81 GHz) millimeter wave have been put to practical use in order to detect an artificial object, such as an automobile, and a pedestrian (human) while separating the artificial object and pedestrian from each other.
As a millimeter-wave radar of this type, a frequency modulated-continuous wave (FM-CW) system has been widely used. In the FM-CW system, a frequency modulated continuous wave is transmitted as a radar signal, and a reflection signal from a target object is received. A relative velocity and relative distance of the target object are then detected based on a frequency difference between the transmitted and received signals. The FM-CW system is described in Patent Literature (hereinafter referred to as “PTL”) 1 and PTL 2, for example.